1. Field of the Invention
This invention relates in general to railcars and, more particularly, to railcar yokes for a coupler system.
2. Brief Description of the Related Art
Railcar couplers are disposed at each end of a railway car to enable joining one end of such railway car to an adjacently disposed end of another railway car. The engageable portion of each of these couplers is known in the railway art as a knuckle. For example, railway freight car coupler knuckles are taught in U.S. Pat. Nos. 4,024,958; 4,206,849; 4,605,133; and 5,582,307.
Typically, adjacent railway cars are joined by heavy shafts extending from each car, known as couplers, and, generally, each coupler is engaged with a yoke housing a shock-absorbing element referred to as the draft gear. The type-E coupler is the standard coupler for railway freight cars. The type-E coupler has standard specifications such that producers making a type-E coupler adhere to a standard specification, so that the standard railway car couplers are completely interchangeable, regardless of the manufacturer. In addition, adherence to a standard also enables couplers from any one manufacturer to be able to be readily joined to couplers from any other domestic manufacturer. The Association of American Railroads (“AAR”) has adopted standards for railway couplers. The coupler must include specific geometry and dimensions that allow it to receive a knuckle, and the geometry must be such that the knuckle is allowed to freely operate when coupling and uncoupling railway cars. These dimensions and features of the coupler may be checked for compliance with AAR standards by using gauges, which are applied to the coupler to verify the coupler dimensions or parameters are within an allowable variation or tolerance range.
Couplers have a particular life, and in instances may fail. In many cases when a railcar coupler fails, a replacement coupler must be carried from the locomotive at least some of the length of the train, which may be up to 25, 50 or even 100 railroad cars in length. The repair of a failed coupler can be labor intensive, can sometimes take place in very inclement weather and can cause train delays.
The yoke is a generally elongated structure having two side sections that extend from and join with a tail portion. The side sections are also known and referred to as “straps”. The side sections or straps are joined at the opposite end by a head portion where the yoke is joined to the coupler with a securing component, such as a key or pin. The yoke generally has a pocket formed by the straps and a rear wall, and a draft gear is positioned between the straps of the yoke, and between the tail portion and the head portion. The best-known yokes are the E-type and F-type. The E-type yoke is governed by AAR standards that include the AAR S-143 Standard, SY 40AE, Y40 or YS93AE, for a 24⅝ inch gear pocket, although there are some tolerances that the pocket may have, as permitted by the standards. A typical E-type yoke has straps that are 5 inches. The F-type yoke is governed by the S-149 standard and the Y45 standard. Although there are other differences between E-type and F-type yokes, a primary difference is the design and orientation of the pin or key used to join the coupler to the yoke.
Typical yokes contain apertures in the yoke head portion, which also may be known as the key slots or pin bores by which a coupler is joined to the yoke with the installation of a key or pin through the slot or bore to connect the yoke and coupler. Adjacent railcars, when coupled together and in motion, place tension on the yoke and compressive forces are transferred to bearing surfaces at opposed ends of the yoke where the draft gear is housed.
Adjacent freight cars are separated in accordance with standard specifications which includes an allowance for a specified yoke length. In accordance with applicable AAR standards, typically, E-type and F-type yokes, respectively, may have a length of 41⅛″ or 37½″.